It is a recognised that most piston engines are inherently inefficient. A number of factors are responsible for this inefficiency including the motion of the pistons, and the fact that at times each piston is either at rest or in a drag state which therefore reduces the amount of energy available at the crank of the engine. Also energy is required to move a piston to the top of its bore during each compression or pump stroke.
A further cause of inefficiency in an existing internal combustion engine is that energy is used to operate gears, cams and other equipment necessary to enable the engine to function. This use of energy results in reduced efficiency, and in the final analysis only a small percentage of input energy is transferred as output from an engine.
Rotary type engines overcome some of the above problems. However, rotary engines are complex and sealing problems exist between the moving parts. While rotary engines have dramatically changed the design of standard piston and cylinder engines they have resulted in complex sealing and design problems which can result in reliability problems.
Hybrid engines are another type of known engine. An example of a hybrid engine is described in EP0964136, which is a rotary type engine configuration with the engine's block defining a cylindrical rotor having a plurality of bores which open to combustion chambers near the periphery of the engine block. A piston is disposed in each bore. Each piston has its own crank with rotation transferred to the engine block/rotor via a planetary gear arrangement. Inlet ports, spark plugs and outlet ports are arranged around the periphery of the engine housing in the same manner as a conventional rotary engine. The advantage claimed for this configuration of engine is that the power/movement of the pistons is almost completely converted to rotational movement of the engine and thus it produces a greater power output per size/weight than a conventional piston engine. A further advantage is that the rotary nature of the engine does away with the need to employ valves and thus the associated problem of valve damage in conventional engines is eliminated. Such an engine still suffers from considerable sealing problems and losses in the planetary gearbox linking the piston rods to the rotor.
Another hybrid engine is described in AU 8496/27. This engine is of a type that has a continuously rotating group of cylinders disposed tangentially on a main rotatable member. Corresponding pistons are intermittently rotating. The pistons are attached to piston levers pivoted about the centre of rotation. In order to achieve correct operation of this engine the pistons must be locked against movement in either direction during combustion so that energy can be transferred to the rotatable member via the cylinders. After combustion the piston must accelerate at twice the speed of the rotary member in order to move back to top dead centre for the next combustion stroke. A sophisticated arrangement of gears and levers is therefore required to operate the pistons in this manner. Because the pistons must travel at twice rotational speed the engine's maximum speed is limited by the ability to move the pistons from standstill to top dead centre.
As well as the above mentioned disadvantages, in existing piston engines, the time the piston spends at the top and bottom of its stroke is very short as the crankshaft operates to change direction at the instant that the extreme of piston travel is reached. This reduces dwell and leads to incomplete burning of gases in the combustion chamber. These incompletely burnt gases are expelled in the exhaust resulting in inefficiencies in the engine and pollution of the atmosphere.
Accordingly it is an object of the present invention to provide an engine which is efficient and economical to run. It is a further object of the present invention to provide an engine which has high rotational inertia and torque relative to its size and weight.
It is still a further object of the present invention to provide an engine which can be controlled in a variety of ways to meet a variety of functional needs.
Yet a further object of the present invention is to provide an engine which ameliorates some of the disadvantages of known engines, or at least provides the public with a useful alternative choice.